In the related art, for example, a device described in Japanese Patent No. 5589869 (Reference 1) has been known as a vehicle door handle device. The vehicle door handle device uses two electric wires (connection wires) to be connected to an ECU, and these two electric wires are used for the power supply (driving) of an antenna, for the power supply of a detection member, for the outputting of the detection signal, and for the detection of a driving state of the antenna. Particularly, in order to detect the driving state of the antenna, it has been suggested that a resonance voltage of the antenna is used.
In Reference 1, since the resonance voltage is used to detect of the driving state of the antenna, it is necessary to set the resonance voltage to be equal to or less than a rated voltage. Accordingly, it is necessary to increase the size of the antenna as the Q factor of the antenna may not be increased.